Method of making heat treated coated article using diamond-like carbon (DLC) coating and protective film

ABSTRACT

There is provided a method of making a heat treated (HT) coated article to be used in shower door applications, window applications, or any other suitable applications where transparent coated articles are desired. For example, certain embodiments of this invention relate to a method of making a coated article including a step of heat treating a glass substrate coated with at least a layer of or including diamond-like carbon (DLC) and an overlying protective film thereon. In certain example embodiments, the protective film may be of or include an oxide of zinc. Following and/or during heat treatment (e.g., thermal tempering, or the like) the protective film may be removed. Other embodiments of this invention relate to the pre-HT coated article, or the post-HT coated article.

Certain embodiments of this invention relate to a method of making aheat treated (HT) coated article to be used in shower door applications,window applications, tabletop applications, or any other suitableapplications. For example, certain embodiments of this invention relateto a method of making a coated article including a step of heat treatinga glass substrate coated with at least a layer comprising diamond-likecarbon (DLC) and an overlying protective film thereon. In certainexample embodiments, the protective film may be of or include an oxideof zinc. Following and/or during heat treatment (e.g., thermaltempering, or the like) the protective film may be entirely or partiallyremoved. Other embodiments of this invention relate to the pre-HT coatedarticle, or the post-HT coated article.

BACKGROUND OF THE INVENTION

Coated articles such as transparent shower doors and IG window units areoften heat treated (HT), such as being thermally tempered, for safetyand/or strengthening purposes. For example, coated glass substrates foruse in shower door and/or window units are often heat treated at a hightemperature(s) (e.g., at least about 580 degrees C., more typically fromabout 600-650 degrees C.) for purposes of tempering.

Diamond-like carbon (DLC) is sometimes known for its scratch resistantproperties. For example, different types of DLC are discussed in thefollowing U.S. Pat. Nos.: 6,303,226; 6,303,225; 6,261,693; 6,338,901;6,312,808; 6,280,834; 6,284,377; 6,335,086; 5,858,477; 5,635,245;5,888,593; 5,135,808; 5,900,342; and 5,470,661, all of which are herebyincorporated herein by reference.

It would sometimes be desirable to provide a window unit or other glassarticle with a protective coating including DLC in order to protect itfrom scratches and the like. Unfortunately, DLC tends to oxidize andburn off at temperatures of from approximately 380 to 400 degrees C., asthe heat treatment is typically conducted in an atmosphere includingoxygen. Thus, it will be appreciated that DLC as a protective overcoatcannot withstand heat treatments (HT) at the extremely high temperaturesdescribed above which are often required in the manufacture of vehiclewindows, IG window units, glass table tops, and/or the like.

Accordingly, those skilled in the art will appreciate that a need in theart exists for a method of providing heat treated (HT) coated articleswith a protective coating (one or more layers) comprising DLC. A needfor corresponding coated articles, both heat treated and pre-HT, alsoexists.

BRIEF SUMMARY OF EXAMPLES OF INVENTION

Certain example embodiments of this invention relate to a method ofmaking a heat treated (HT) coated article to be used in shower doorapplications, window applications, tabletop applications, or any othersuitable application. For example, certain embodiments of this inventionrelate to a method of making a coated article including a step of heattreating a glass substrate coated with at least a layer comprisingdiamond-like carbon (DLC) and an overlying protective film thereon. Incertain example embodiments, the protective film may be of or include anoxide of zinc. Following and/or during heat treatment (e.g., thermaltempering, or the like) the protective film may be entirely or partiallyremoved. Other embodiments of this invention relate to the pre-HT coatedarticle, or the post-HT coated article.

In certain example embodiments of this invention, there is provided amethod of making a heat treated coated article, the method comprising:providing a glass substrate; forming at least one layer comprisingdiamond-like carbon (DLC) on the glass substrate; forming a protectivefilm comprising zinc on the glass substrate over at least the layercomprising DLC; heat treating the glass substrate with the layercomprising DLC and the protective film comprising zinc thereon so thatduring the heat treating the protective film prevents significantburnoff of the layer comprising DLC, wherein the heat treating comprisesheating the glass substrate to temperature(s) sufficient for thermaltempering, heat strengthening, and/or heat bending; and removing atleast part of the protective film comprising zinc during and/or aftersaid heat treating.

In other example embodiments of this invention, there is provided amethod of making a heat treated coated article, the method comprising:providing a glass substrate; forming at least one layer comprisingcarbon on the glass substrate; forming a protective film comprising zincon the glass substrate over at least the layer comprising carbon; heattreating the glass substrate with the layer comprising carbon and theprotective film comprising zinc thereon so that during the heat treatingthe protective film prevents significant burnoff of the layer comprisingcarbon, wherein the heat treating comprises heating the glass substrateto temperature(s) sufficient for thermal tempering, heat strengthening,and/or heat bending; and removing at least part of the protective filmcomprising zinc during and/or after said heat treating.

In still further example embodiments of this invention, there isprovided a coated article comprising: a glass substrate supporting atleast one layer comprising diamond-like carbon (DLC); a protective filmcomprising zinc oxide on the glass substrate over at least the layercomprising DLC; and wherein the protective film comprising zinc oxide isoxidation graded so that the protective film is more oxided (oxidized)at a location further from the layer comprising DLC than at a locationcloser to the layer comprising DLC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view of a coated article, prior toand following heat treatment, according to an example embodiment of thisinvention.

FIG. 2 is a schematic cross sectional view of a coated article, prior toand following heat treatment, according to another example embodiment ofthis invention.

FIG. 3 is a schematic cross sectional view of a coated article, prior toand following heat treatment, according to another example embodiment ofthis invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Referring now more particularly to the accompanying drawings in whichlike reference numerals indicate like parts throughout the severalviews.

Certain example embodiments of this invention relate to methods ofmaking coated articles that may use heat treatment (HT), wherein thecoated article includes a coating (one or more layers) includingdiamond-like carbon (DLC). In certain instances, the HT may involveheating a supporting glass substrate, with the DLC thereon, totemperature(s) of from 550 to 800 degrees C., more preferably from 580to 800 degrees C. (which is well above the burn-off temperature of DLC).In particular, certain example embodiments of this invention relate to atechnique for allowing the DLC to withstand such HT withoutsignificantly burning off during the same. In certain embodiments, asacrificial protective film is formed on the glass substrate over theDLC so as to reduce the likelihood of the DLC burning off during HT.Thus, the majority (if not all) of the DLC remains on the glasssubstrate, and does not burn off, during the HT. Following HT, thesacrificial protective layer may or may not be removed in differentembodiments of this invention.

FIG. 1 is a schematic cross sectional view of a coated article, beforeand after heat treatment, according to an example embodiment of thisinvention. Typically, the coated article on the left side of FIG. 1exists during a stage of manufacture prior to heat treatment (HT), butmay also exist post-HT in certain instances. The coated article shown inFIG. 1 includes glass substrate 1, DLC inclusive layer 11, andsacrificial protective film 17 which may include one or more layers. Incertain example embodiments, the protective film 17 includes first andsecond layers 17 a and 17 b which may be of the same or differentmaterial(s).

Glass substrate 1 is typically of or includes soda-lime-silica glass,although other types of glass may be used in certain instances.

DLC inclusive layer 11 may be from about 5 to 1,000 angstroms (Å) thickin certain example embodiments of this invention, more preferably from10-300 Å thick, and most preferably from 20 to 65 Å thick, possibly fromabout 25-50 Å thick, with an example thickness being about 30 angstroms.In certain example embodiments of this invention, DLC layer 11 may havean average hardness of at least about 10 GPa, more preferably at leastabout 20 GPa, and most preferably from about 20-90 GPa. Such hardnessrenders layer(s) 11 resistant to scratching, certain solvents, and/orthe like. Layer 11 may, in certain example embodiments, be of or includea special type of DLC known as highly tetrahedral amorphous carbon(t-aC), and may be hydrogenated (t-aC:H) in certain embodiments. Incertain hydrogenated embodiments, the t-aC type or any other suitabletype of DLC may include from 1 to 30% hydrogen, more preferably from5-20% H, and most preferably from 10-20% H. This t-aC type of DLCincludes more sp³ carbon-carbon (C—C) bonds than sp² carbon-carbon (C—C)bonds. In certain example embodiments, at least about 30% or 50% of thecarbon-carbon bonds in DLC layer 11 may be sp³ carbon-carbon (C—C)bonds, more preferably at least about 60% of the carbon-carbon bonds inthe layer 11 may be sp³ carbon-carbon (C—C) bonds, and most preferablyat least about 70% of the carbon-carbon bonds in the layer 11 may be sp³carbon-carbon (C—C) bonds. In certain example embodiments of thisinvention, the DLC may have an average density of at least about 2.4gm/cm³, more preferably at least about 2.7 gm/cm³. Example linear ionbeam sources that may be used to deposit DLC inclusive layer 11 onsubstrate 1 include any of those in any of U.S. Pat. Nos. 6,261,693,6,002,208, 6,335,086, or 6,303,225 (all incorporated herein byreference). When using an ion beam source to deposit layer(s) 11,hydrocarbon feedstock gas(es) (e.g., C₂H₂), HMDSO, or any other suitablegas, may be used in the ion beam source in order to cause the source toemit an ion beam toward substrate 1 for forming layer(s) 11. It is notedthat the hardness and/or density of layer(s) 11 may be adjusted byvarying the ion energy of the depositing apparatus.

DLC layer 11 allows the coated article to be more scratch resistant thanif the DLC 11 were not provided. It is noted that while layer 11 is onglass substrate 1 in certain embodiments of this invention, additionallayer(s) may or may not be under layer 11 between the substrate 1 andlayer 11 in certain example embodiments of this invention. Thus, thephrase “on the substrate” as used herein is not limited to being indirect contact with the substrate as other layer(s) may still beprovided therebetween.

For example and without limitation, the layer 11 of or including DLC maybe any of the DLC inclusive layers of any of U.S. Pat. Nos. 6,592,993;6,592,992; 6,531,182; 6,461,731; 6,447,891; 6,303,226; 6,303,225;6,261,693; 6,338,901; 6,312,808; 6,280,834; 6,284,377; 6,335,086;5,858,477; 5,635,245; 5,888,593; 5,135,808; 5,900,342; or 5,470,661 (allof these patents hereby being incorporated herein by reference), oralternatively may be any other suitable type of DLC inclusive layer. DLCinclusive layer 11 may be hydrophobic (high contact angle), hydrophilic(low contact angle), or neither, in different embodiments of thisinvention.

Sacrificial protective film 17 is provided in order to protect DLC layer11 during HT. If film 17 were not provided, the DLC 11 wouldsignificantly oxidize during HT and burn off, thereby rendering thefinal product defenseless against scratching. However, the presence ofsacrificial protective film 17 prevents or reduces the amount of oxygenwhich can reach the DLC 11 during HT from the surrounding atmosphere,thereby preventing the DLC from significantly oxidizing during HT. As aresult, after HT, the DLC inclusive layer 11 remains on the glasssubstrate 1 in order to provide scratch resistance and/or the like.

It has surprisingly been found that the use zinc and/or zinc oxide insacrificial protective film 17 is/are especially beneficial with respectto reducing and/or preventing oxygen diffusion into the DLC during HT.In the FIG. 1 example embodiment of this invention, the protective film17 includes a first zinc inclusive layer 17 a and a second zinc oxideinclusive layer 17 b. The first zinc inclusive layer 17 a may bemetallic, substantially metallic, or substoichiometric zinc oxide indifferent example embodiments of this invention; whereas the second zincoxide inclusive layer 17 b may be of or including zinc oxide in certainexample embodiments of this invention. In certain example embodiments,layer 17 a is more metallic than layer 17 b. In other words, layer 17 bcontains more oxygen than does layer 17 a.

In certain example embodiments of this invention, layer 17 a may be ofor include ZnO_(y) and layer 17 b may be of or include ZnO_(x), wherex>y (i.e., layer 17 b contains more oxygen than layer 17 a). Moreover,in certain example embodiments of this invention, y is from about 0 to0.9, more preferably from about 0.1 to 0.9, even more preferably fromabout 0.1 to 0.8, and possibly from about 0.1 to 0.7. Meanwhile, incertain example embodiments of this invention, x is greater than y, andx is from about 0.3 to 1.0, more preferably from about 0.3 to 0.99, evenmore preferably from about 0.5 to 0.95, and possibly from about 0.6 to0.90. Thus, it will be appreciated that in certain example instances,both layers 17 a and 17 b may be of or include zinc oxide, and bothlayers 17 a and 17 b may be substoichiometric.

Advantageously, it has been found that the use of zinc oxide layer 17 athat is more metallic than zinc oxide layer 17 b surprisingly permitsmore efficient and easier removal of the protective film 17 duringand/or following heat treatment (HT). The different compositions of zincoxide inclusive layers 17 a and 17 b is used to cause different stressesin layers 17 a and 17 b, which stresses are manipulated so as to allowthe film 17 to be more easily removed during and/or following HT. Inparticular, more metallic zinc oxide based layer 17 a may optionally beconsidered a release layer for allowing the film 17 to be easily removedfrom the DLC or substrate during and/or after HT due to its reduced orno oxygen content, whereas the less metallic (and more oxided) zincoxide based layer 17 b may be considered an oxygen blocking layer thatreduces or prevents the DLC from burning off and/or oxidizing during HT.Note also that any gettering layer may be considered an oxygen barrierlayer in certain example instances. In certain example instances, themore oxidic layer 17 b may be considered a blocking/protection layer,for protecting the softer less oxidic getting/barrier layer 17 a duringheat treatment and otherwise. Zinc oxide is a highly advantageousmaterial for film 17 because it can be easily removed (e.g., using waterand/or vinegar) during and/or following HT in a non-toxic manner.Moreover, metallic Zn and/or zinc oxide are also highly advantageous foruse in protective film 17 because the Zn in film 17 acts as a getter foroxygen during HT thereby preventing or reducing the likelihood of theDLC burning off during such HT. In certain example embodiments, duringhigh temperature oxidation the resulting oxide film protects the moremetallic film 17 a from further oxidation; the zinc inclusive layer 17 athat is more metallic has a greater potential increase in volume due tooxidation than does a more oxidized zinc oxide layer, and such anincrease in volume (e.g., during tempering) results in an increase instress permitting more efficient/easier film removal.

As noted above, one or both of layers 17 a and 17 b when of or includingzinc and/or zinc oxide are substoichiometric. This is advantageous foroxygen gettering purposes during HT. If the zinc oxide of the entirefilm 17 is too oxided (i.e., fully stoichiometric) prior to HT, thenoxygen can diffuse through the zinc oxide. However, thesubstoichiometric nature of layer(s) 17 a and/or 17 b permits the zinctherein to getter oxygen during HT, so that at least layer 17 a (andpossibly layer 17 b) does not burn off during HT. It is noted that upperzinc oxide based layer, 17 b may or may not burn off (entirely orpartially) during HT in different example embodiments of this invention.It is noted that another example advantage of substoichiometric zincoxide (compared to fully stoichiometric zinc oxide) is that it can bedeposited (e.g., via sputtering or the like) more quickly. One or bothof layers 17 a, 17 b may be sputter-deposited in a substoichiometricform, in any suitable manner; e.g., by varying oxygen gas flow in thesputtering chamber(s). For example, as one non-limiting example, layer17 a may be sputter-deposited using 10 ml/kW (regarding content ofoxygen gas flow), whereas layer 17 b may be sputter-deposited using 12ml/kW (with remainder of the gas being Ar or the like) in exampleinstances.

Note that one or both of zinc oxide layers 17 a and 17 b may be dopedwith other materials such as Al, N, Zr, Ni, Fe, Cr, Ti, Mg, mixturesthereof, or the like, in certain example embodiments of this invention.

In certain example embodiments of this invention, layer 17 a (e.g., ofzinc or substoichiometric zinc oxide) may be deposited (e.g., viasputtering) so as to be from about 500-20,000 Å thick, more preferablyfrom about 2,000-15,000 Å thick, even more preferably from about2,000-10,000 Å thick, with an example thickness being about 8,000 Å. Incertain embodiments, zinc oxide inclusive layer 17 b may be deposited(e.g., via sputtering) so as to be from about 200-10,000 Å thick, morepreferably from about 500-5,000 Å thick, more preferably from about1,000-3,000 Å thick, with an example thickness being about 2,000 Å. Moremetallic layer 17 a is thicker than less metallic layer 17 b in certainexample embodiments of this invention; layer 17 a may be at least twiceas thick as layer 17 b in certain example instances prior to HT.

FIG. 2 illustrates another example embodiment of this invention. TheFIG. 2 embodiment is the same as the FIG. 1 embodiment discussed above,except that in the FIG. 2 embodiment a barrier layer 6 is providedbetween the glass substrate 1 and the DLC inclusive layer 11. Barrierlayer 6 may be a dielectric in certain example embodiments of thisinvention. Optional barrier layer 6 is for preventing or reducing oxygenand/or sodium (Na) from migrating from the glass 1 into the DLC 11during HT. In this respect, such an optional barrier layer 6 may improvethe overall optical characteristics of the coated article post-HT.Barrier layer 6 may be of or include silicon oxide, silicon nitride,silicon oxynitride, and/or the like, although other barrier materialsmay also be used. Barrier layer(s) 6 is formed on the glass substrate 1via sputtering, or via any other suitable technique. Barrier layer 6 maybe from about 10 to 1,000 Å thick in certain example embodiments, morepreferably from 50 to 500 Å thick, and most preferably from 50 to 200 Åthick.

FIG. 3 illustrates another example embodiment of this invention. TheFIG. 3 embodiment is the same as the FIG. 1 embodiment (or even the FIG.2 embodiment if barrier layer 6 is used, which may be the case in theFIG. 3 embodiment), except that instead of two discrete layers 17 a and17 b the protective film 17 is made of one layer that is oxidationgraded (continuously or non-continuously) through its thickness. In theFIG. 3 embodiment, the film 17 is provided in a manner so that the film17 includes more oxygen at a location further from the DLC layer 11 thanat another location in the film closer to the DLC layer 11. Note thatthe film 17 in the FIG. 1-2 embodiments may also be considered oxidationgraded because the overall film 17 is more oxided in layer 17 b furtherfrom the DLC 11 than in layer 17 a closer to the DLC 11. However, in theFIG. 3 embodiment, it is also possible for continuous or substantiallycontinuous oxidation grading to occur through the entire orsubstantially entire film 17 in certain example instances.

An example process of manufacturing a coated article will now bedescribed, with reference to FIGS. 1-3. Initially, glass substrate 1 isprovided, and at least one barrier layer 6 (e.g., silicon oxide, siliconnitride, silicon oxynitride, or the like) may optionally be sputtered ona surface thereof. Optionally, a multi-layer solar control coating (notshown) may be deposited (e.g., via sputtering) on the surface of theglass substrate 1 opposite the barrier layer 6. At least one layer 11 ofor including DLC is deposited (e.g., via ion beam deposition) on theglass substrate 1, over at least the optional barrier layer 6 ifpresent. Then, protective film 17, e.g., including layers 17 a and 17 b,is deposited on the substrate 1 over the DLC inclusive layer 11.Protective film 17 may be deposited via sputtering, CVD, ion beamdeposition, or any other suitable technique. Optionally, a thinprotective layer comprising DLC, silicon nitride, aluminum nitride, orsilicon aluminum nitride (not shown), may be provided over sacrificialfilm 17 prior to HT, for durability and/or oxygen barrier purposes.

As shown in FIGS. 1-2, the glass substrate 1 with films 6 (optional), 11and 17 thereon is then heat treated (HT) for purposes of thermaltempering, heat bending, heat strengthening, and/or the like. At leastpart of this HT may be conducted, for example, in an atmosphereincluding oxygen as known in the art at temperature(s) of from 550 to800 degrees C., more preferably from 580 to 800 degrees C. (i.e.,temperature(s) above the burn-off temperature of DLC). The HT may lastfor at least one minute, more preferably from 1-10 minutes, in certainexample non-limiting embodiments of this invention. During HT, thepresence of protective film 17 protects DLC inclusive layer 11 from theHT and prevents layer 11 from significantly oxidizing and/or burning offdue to significant oxidation during the HT. While in some instances someof layer 11 may burn off during HT, the majority if not all of DLCinclusive layer 11 remains on the substrate 1 even after the HT due tothe presence of protective film 17.

A significant advantage associated with using zinc and/or zinc oxide infilm 17 is its ease of removal after HT. Protective layers such assilicon nitride are sometime undesirable since they require complexetching in order to remove the same after HT. On the other hand, it hasbeen found that when film 17 is made of zinc and/or zinc oxide, solublein vinegar and/or water (possibly only water with no vinegar required incertain preferred embodiments), the application of vinegar and/or waterallows portions of film 17 remaining after HT to be easily removed in anon-toxic manner. Again, in certain example embodiments, it is possibleto remove the zinc oxide with only water (no vinegar needed) in certaininstances, which is advantageous from a cost and processing point ofview. In certain example instances, rubbing with such liquids may beespecially beneficial in removing film 17 after HT when the coatedarticle is still warm therefrom (e.g., when the film 17 is from about80-200 degrees C., more preferably from about 100-180 degrees C.;although the removal of film 17 may also take place at room temperaturein certain example embodiments).

After film 17 has been removed, the remaining coated article is shown atthe right side of FIGS. 1-2, and includes an outer layer comprisingscratch resistant DLC. The aforesaid processes are advantageous in thatthey provide a technique for allowing a coated article including aprotective DLC inclusive layer 11 to be heat treated without the DLClayer 11 burning off during such HT. In other words, it becomes possibleto provide a protective DLC inclusive layer 11 on a heat treated (e.g.,thermally tempered) product in a commercially acceptable manner.

According to certain example embodiments of this invention, coatedarticles herein lose no more than about 15% of their visibletransmission due to HT, more preferably no more than about 10%.Moreover, monolithic coated articles herein preferably have a visibletransmission after HT of at least about 50%, more preferably of at leastabout 60 or 75%.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

-   -   1-22. (canceled)

23. A method of making a heat treated coated article, the methodcomprising: providing a glass substrate; forming at least one layercomprising carbon on the glass substrate; forming a removable protectivefilm on the glass substrate over at least the layer comprising carbon,the removable protective film comprising a first layer comprising zincoxide and a second layer comprising zinc oxide, wherein the first layercomprising zinc oxide is more metallic than is the second layercomprising zinc oxide, and wherein the first layer comprising zinc oxideis between the layer comprising carbon and the second layer comprisingzinc oxide; heat treating the glass substrate with the layer comprisingcarbon and the protective film thereon so that during the heat treatingthe protective film prevents significant burnoff of the layer comprisingcarbon, wherein the heat treating comprises heating the glass substrateto temperature(s) sufficient for thermal tempering, heat strengthening,and/or heat bending; and removing at least part of the protective filmcomprising zinc during and/or after said heat treating.
 24. The methodof claim 23, wherein the removable protective film is formed on theglass substrate via sputtering.
 25. The method of claim 23, furthercomprising forming a barrier layer comprising silicon oxide and/orsilicon nitride on the glass substrate so as to be located between atleast the glass substrate and the layer comprising carbon.
 26. Themethod of claim 23, wherein the heat treating comprises heating theglass substrate with the layer comprising carbon and the protective filmthereon using at least temperature(s) of at least 580 degrees C.
 27. Themethod of claim 23, wherein the layer comprising carbon comprises DLC.28. A method of making a heat treated coated article, the methodcomprising: providing a glass substrate; forming at least one layercomprising carbon on the glass substrate; forming a removable protectivefilm on the glass substrate over at least the layer comprising carbon,the removable protective film comprising first and second inorganiclayers, the first inorganic layer comprising zinc oxide and beinglocated between the layer comprising DLC and the second inorganic layer;heat treating the glass substrate with the layer comprising carbon andthe protective film thereon so that during the heat treating theprotective film prevents significant burnoff of the layer comprisingDLC, wherein the heat treating comprises heating the glass substrate totemperature(s) sufficient for thermal tempering, heat strengthening,and/or heat bending, and wherein the first inorganic layer comprisingzinc oxide and the second inorganic layer substantially remain on theglass substrate protecting the layer comprising DLC during said heattreating; and removing the first inorganic layer comprising zinc oxideand the second inorganic layer after said heat treating.
 29. The methodof claim 28, wherein the heat treating comprises heating the glasssubstrate with the layer comprising carbon and the protective filmthereon using at least temperature(s) of at least 580 degrees C.